Liquid crystal displays are commonly used as display devices for compact electronic apparatuses because they not only provide good quality images with little power, but also are very thin. The liquid crystal in a liquid crystal display does not emit any light itself. The liquid crystal has to be lit by a light source so as to clearly and sharply display text and images. Thus, a backlight module including an illuminant is generally needed for a liquid crystal display. In general, there are two types of backlight modules, which are distinguished according to where the illuminant is located in the backlight module. The two types are the side-edge-type backlight module and direct-type backlight module.
The use of the liquid crystal display is becoming increasingly widespread, and large size liquid crystal displays such as liquid crystal televisions are becoming very popular. One major solution to enhancing the total emitting luminance of a large size liquid crystal display is to increase the number of illuminants utilized in the backlight module. It is much easier to increase the number of illuminants of a direct-type backlight module than to increase the number of illuminants of a side-edge-type backlight module. Accordingly, direct-type backlight modules have become the mainstream backlight module of large size liquid crystal displays.
Referring to FIG. 8, a related art backlight module 10 includes a frame 11, a reflecting plate 13, a diffuser 15, a plurality of linear light tubes 17, and two supporting members 19 for supporting the diffuser 15. The frame 11 forms a receiving space (not labeled) to accommodate the reflecting plate 13, the diffuser 15, the linear light tubes 17, and the supporting members 19. The light tubes 17 are parallel to each other and are disposed between the reflecting plate 13 and the diffuser 15. Each of the two supporting members 19 is disposed between two corresponding light tubes 17. A bottom end of each supporting member 19 is fixed to a bottom plate of the frame 11, and a top end of each supporting member 19 contacts the diffuser 15 in order to avoid distortion of the diffuser 15.
Even after the backlight module 10 has been assembled, the diffuser 15 is typically not very tightly integrated with the frame 11. Therefore the diffuser 15 may repeatedly shift or shake when the backlight module 10 is subjected to vibration such as during transportation. The diffuser 15 typically strikes the supporting members 19, and the supporting members 19 scrape the diffuser 15. Thus, the optical characteristic of the diffuser 15 is impaired, and the uniformity of light emitting from the backlight module 10 during operation is reduced.
What is needed, therefore, is a backlight module that can overcome the described limitations.